Green building is the practice of increasing the efficiency with which buildings use resources — energy, water, and materials — thereby reducing a building’s impact on human health and the environment through better siting, design, construction, operation, maintenance, and deconstruction. This practice can also be referred to as sustainable design or green architecture. Green buildings are designed to reduce the overall impact of the built environment on human health and the natural environment by efficiently using energy, water, and other resources, protecting occupant health, improving employee productivity in commercial buildings, and reducing waste, pollution, and environmental degradation. Sustainability is a related concept that is integral to green building. Effectively using the concepts of sustainability while building will lead to reduced operating costs, improved occupant health, and reduced environmental impact.

Environmental impact

Green building practices aim to reduce the environmental impact of buildings. Buildings account for a large amount of land use, energy and water consumption, and air and atmosphere alteration. In the United States, more than 2,000,000 acres (8,100 km2) of open space, wildlifehabitat, and wetlands are placed under anthropogenic development each year. According to the U.S. Department of Energy, residential and commercial buildings accounted for 38.9 percent of all primary energy consumed in the United States in 2006 (20.9 percent in residential buildings and 18 percent in commercial buildings). Buildings also accounted for 19 percent of all natural gas used, five percent of all petroleum used, and 74.2 percent of all electricity used in 2006. In 2007, according to the United States Energy Information Administration, residential buildings in the U.S. were responsible for effectively contributing 1249.5 million metric tons of carbon dioxide to the Earth's atmosphere. The same study showed that commercial buildings in the U.S. emitted 1087.4 million metric tons of carbon dioxide.

Green building practices

Green building brings together a vast array of practices and techniques to reduce and attempt to eliminate the impacts of buildings on the environment and human health. Green building often emphasizes taking advantage of renewable resources or methods of reduced energy use. Effective green buildings are more than just a random collection of environmental friendly technologies. They require careful, systemic attention to the full life cycle impacts of the resources embodied in the building, as well as to the resource consumption and pollution emissions over a building's complete life cycle. The U.S. Department of Energy suggests taking a whole building design approach when planning out the design of the building. Instead of the traditional process, which is to construct the building so that it meets local codes, whole building design requires that a team of professionals meet to think about the building and all of its components as a whole. They must consider what is best for the building under their given budget, and they must also consider which green building technologies are most cost effective and efficient for their design.

Green building materials

Building materials typically considered to be 'green' include rapidly renewable plant materials like bamboo and straw, adobe clay, lumber from forests certified to be sustainably managed, recycled stone, recycled metal, and other products that are non-toxic, reusable, renewable, or recyclable. Additionally, building materials should be extracted and manufactured locally to the building site to minimize the energy used in their transportation.

Cost of green building

The cost of building green is dependent upon many factors, including location, size, technology, access to waste management, climate, and local and regional codes. According to a cost analysis report of green building from 2004, the cost of building sustainably depends on the size and magnitude of the project, as would the cost of a regular building. The United States Green Building Council (USGBC) claims that the benefits of building to be Leadership in Energy and Environmental Design (LEED) certified include an eight to nine percent decrease in operating costs, a 7.5% increase in building values, and a 3.5% increase in occupancy. The National Resources Defense Council also claims that becoming LEED certified allows one to to take advantage of government incentives. Building with the goal of becoming LEED certified does cost more money, however. Most studies that claim that constructing a green building costs only a very small percent more than building a traditional building do not factor in the costs that come with the planning of the building. Most architects and design professionals are not familiar with green building, so time and money must be spent on educating them. Even simply pursuing LEED certification costs money as well. The cost of the building itself is not that much more than a traditional building, but the cost of the construction and planning for the building does cost more than doing so for a conventional building. However, in most cases, the long term financial savings from reduced energy use mitigates the initial higher costs of constructing the building.

Reduced energy use

A building can greatly lower its utility bills while decreasing its impact on the environment by incorporating technologies that reduce energy use. Energy use can be reduced in several ways. Builders can use highly efficient insulation materials to strengthen the building envelope, lessening the need for heat in cold weather and air conditioning in warm weather. High efficiency windows also help to strengthen the barrier between the building and the elements. Hybrid solar lighting collects light from the sun and sends it through optical fibers into buildings where it combines with electrical light in hybrid light fixtures. This reduces the need for electricity to provide light. Another way to lessen the need of artificial light is to orient windows so that they let in as much natural light as possible. Heating, ventilating, and air conditioning (HVAC) systems are energy efficient systems that can be used to control and maintain the temperature and quality of air inside a building. The use of HVAC systems leads to reduced use of fans, conventional heating systems, and improved occupant health (because the air inside is cleaner).

Human health issues

Green building technology can offer numerous advantages to the occupants of the resulting structures including benefits in: (a) indoor air quality; (b) sound levels; and (c) beneficial illumination levels. Indoor air quality is improved by avoiding adhesives and other chemicals that produce deleterious off-gassing, especially in the first several years of a building's use. There are other potential benefits if materials are chosen to minimize life-cycle cleaning activity, especially use of aerosols and other chemicals that can irritate respiratory systems. In addition, screening of building stone materials can avoid substances that produce harmful radon gas; correspondingly, site surveys to avoid radon emanating from subsoils will remove risks of exposure to radon.

Improved building skin insulation favors the conservation of energy, but it also reduces the penetration of externally generated noise pollution, and thus protects building occupants from excessive sound levels from aircraft, motor vehicle and other noise sources. This outcome improves cardiovascular health and statistically reduces headache incidence and hearing degradation.

Avoidance of over-illumination produces significant energy cost savings, but also enhances the health and well being of building occupants. Considerable research has demonstrated that most buildings beginning in the 1950s were designed with excessive installed lighting intensity, partly due to heavy influence of lighting manufacturing industry influences. The benefits of designing buildings to avoid over-illumination include reduction of reported incidence of headaches, improvement of workplace efficiency and statistical improvement in cardiovascular health. Reduction in lighting that emanates from a given property to off-site locations also reduces light pollution to neighborhood residents.

On the other hand, some types of over-zealous use of building insulation can lead to outcomes that reduce the ability of the building interior to exchange air with the outside, and in some cases can increase the risk of radon mortality or other impacts of indoor air pollution.

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Renewable energy

Renewable energy comes from natural resources that can either regenerate itself within a human time scale or is inexhaustible. Solar power is a form of renewable energy that is useful in buildings. There are many technologies that make it possible to capture sunlight and turn it into useful energy. Photovoltaics (often called PV) uses semi-conductors to convert sunlight directly into electricity. PV can be used to produce very small or very large amounts of electric power, making it useful and cost effective in buildings. Building Integrated Photovoltaics (BIPV) are materials that replace the conventional materials used in the roof or skylight of a building. Using BIPV also strengthens the building envelope and provides the building with a form of renewable energy. Passive solar design uses an array of techniques to obtain energy from the sun which can be used without any conversions. Some examples of passive solar technologies include using materials that absorb and store the sun’s heat which can be used to heat the building, or using strategically placed windows to provide replace the need for artificial light. Active solar designs use several different technologies to capture sunlight, which is then converted into useful energy through a generator. Active solar can be used for space heating or for water heating.

Reduced waste

Green architecture seeks to reduce waste of energy, water and materials. There are three main phases of a building’s life cycle that must be considered when talking about waste reduction: construction, operation, and deconstruction or removal. During the construction phase, one goal is to reduce the amount of material going to landfills. This can be done by recycling goods instead of putting them in landfills or by buying only enough to complete the job. Another goal is to conserve energy during the construction process. During the operation phase, there are many things a building and its occupants can do to reduce the amount of waste the building produces. On-site solutions such as compost bins can reduce matter going to landfills.

To reduce the impact on wells or water treatment plants, several options exist. "Greywater", wastewater from sources such as dishwashing or washing machines, can be used for subsurface irrigation, or if treated, for non-potable purposes, like flushing toilets and washing cars. Rainwater collectors can be used for similar purposes.Another way to assimilate waste is to convert it into fertilizer. This cuts down on the use of centralized wastewater treatments, which can be costly and use a lot of energy. By collecting human waste at the source and running it to a semi-centralized biogas plant with other biological waste, liquid fertilizer can be produced. Practices like these provide soil with organic nutrients and create carbon sinks that remove carbon dioxide from the atmosphere, offsetting greenhouse gas emission, proving to be beneficial to the atmosphere and waste assimilation. In the demolition phase, any and all recyclable materials should be recycled and reused, not put into landfills.

Regulatory programs

Many countries are making an effort to encourage green building through a multitude of programs and incentives. In Australia, a program called First Rate has been instituted to increase energy efficiency in residential buildings. Another program called the Green Building Council of Australia (GBCA) has developed a green building standard known as Green Star that examines the environmental design and impact of a building.

USGBC and LEED

The United States has recently developed a similar organization called the U.S. Green Building Council (USGBC), which is a non-profit trade organization that promotes sustainability in how buildings are designed, built, and operated. The USGBC also developed a rating system called Leadership in Energy and Environmental Design (LEED), which, using a point system, certifies buildings environmentally sustainable. The USGBC works closely with key industry and research organizations as well as with federal, state, and local government agencies. Canada has adopted the LEED program as well as instituted their own set of guidelines which they call R-2000. R-2000 offers incentives to builders who meet their standards of energy efficiency and sustainability. These rating mechanisms are a start on building ratings, but do not take into full account the panoply of design decisions available to building architects and engineers.